Drives having rotors which can move along a path are used, inter alia, in automation technology. As a rule, the rotors are guided along the path by a guide system. Such a guide system can comprise, for example, guide rails which are arranged along the path and rollers which are mounted on the carriage and roll on the guide rails. Such drives are often embodied as linear motors and comprise drive magnets which are arranged on the rotors and which interact with drive coils which are arranged along the path. The rotors of the drive can then be moved or driven by applying a current to the drive coils, with the result that the drive coils generate a suitable magnetic field which propagates along the path.
Such drives comprise as a rule a position-detection system which detects the longitudinal position of the rotors along the path and transmits it to a controller of the drive. Such a position-detection system permits, inter alia, open-loop or closed-loop control of the movement of the rotors according to a predefined control program. Inter alia, magnetic, optical or inductive position-detection systems can be used as the position-detection systems. An inductive position-detection system is disclosed, for example, in German laid-open patent application DE102012204917A1.
The use of linear motors in automation technology permits, inter alia, production goods in a fabrication system to be transported flexibly and independently of one another. A linear motor, which makes independent movement of individual rotors possible, permits, for example, production goods which are transported by the rotors to be grouped during transportation, in order to be able to combine them in common packaging.
The operating state of such a drive is as a rule monitored continuously in order to be able to detect faults of the drive or failures in the production system. Within the scope of the monitoring of the operating state, it is possible, inter alia, to detect loading of a rotor with a payload, a weight of a transported payload or wear of the drive, for example of the guide system which guides the rotors. For this purpose, as a rule sensors are used which are arranged along the path or on the rotors and transmit data to a controller which monitors the fabrication process. The sensors may be, inter alia, photoelectric barriers, Hall sensors or contact sensors, for example stop sensors. Such a system is previously known, for example, from DE102011003682A1.
A disadvantage of the use of such sensors is, inter alia, that they have to be arranged along the path in addition to the drive components, which results in increased costs and greater expenditure on installation. For example, the sensors for monitoring the operating state therefore have to be connected separately by cable to the controller. In particular, in the case of an arrangement of the sensors on the rotor, the problem of a transmission of data to the positionally fixed controller arises, which arrangement requires either the rotors to be connected by cable or active cableless data transmission devices on the rotors to be carried along. A further disadvantage is often also that the drive has to be stopped and the production interrupted in order to determine the operating state, for example to determine wear on the guide system by regular inspection.